The large-scale manufacture of ammonia and its derivative compounds has been performed since the early twentieth century according to a process developed by HABER and others.
The original process, substantially unmodified to the present day, begins with a fuel source, such as coke from bituminous coal or lignite. This fuel is blasted to incandescence and steam is passed through the fuel bed, eventually yielding a mixture of carbon dioxide and hydrogen gases.
The carbon dioxide must be separated from the hydrogen before the synthesis of ammonia can take place. This is accomplished by directing the gas mixture into a potassium carbonate/potassium bicarbonate loop.
The loop must be kept in constant operation, even when the rest of the ammonia plant is shut down. In the loop, the gaseous mixture of hydrogen and carbon dioxide is contacted with cold potassium carbonate aqueous solution. This results in the production of an aqueous potassium bicarbonate solution. Free hydrogen gas is removed and the potassium bicarbonate solution is then heated to approximately 130.degree. C. to regenerate potassium carbonate by evolving carbon dioxide and water vapor. The carbon dioxide and water vapor are vented to the atmosphere. The hot potassium carbonate solution is cooled by means of a heat exchanger, and the cooled solution is recycled. The separated hydrogen gas is combined with a suitable source of nitrogen such that the ratio of hydrogen to nitrogen is approximately 3:1. The hydrogen and nitrogen enter a synthesis loop where they pass over a catalyst in a high-pressure ammonia converter where the ammonia is formed.
Additional useful compounds can also be produced from the ammonia. For example, ammonium sulfate produced by treating the ammonia with sulfuric acid.
Should the potassium carbonate loop in the ammonia manufacture process have to be shut down because of trouble upstream or downstream of the loop, or because of lack of fuel or other material, considerable time and expense are spent in restoring the potassium carbonate cycle to normal operation.
Moreover, though ammonia and its chemical derivatives are very useful chemical compounds, a great deal of energy has to be expended in their manufacture. It would thus be desirable to provide a technique for reducing the energy needed to manufacture a given quantity of ammonia, as well as minimizing the amount of energy wasted when cycling the potassium carbonate loop when the rest of the system is shut down.